Aspectos sedimentológicos de arenas eólicas del Pleistoceno tardío-Holoceno de la provincia de La Pampa

the main goal of this paper is to analyze the provenience of sandy eolian deposits of the central eastern part of la pampa province. considering present eolian models proposed by different authors, the hypothesis tested in this paper is that eolian sediments are the result of deflation of alluvial deposits from the bermejo-desaguadero-salado-curacó fluvial system. with this purpose in mind, three case studies were selected (la pastoril-santa isabel, toay and general acha) (fig. 1). the analysis was made following the concept of spatial scale hierarchy which considered the geological and general environmental setting of the studied areas along with fundamental geomorphological features of the analyzed dune systems. this was complemented by the stratigraphic survey of selected sections from which 20 samples were collected for sedimentological analysis (grain-size and mineralogy). also, due to the lack of information, three samples were collected from the present desaguadero fluvial system for general characterization. at the regional scale two main geoforms were identified: an extensive plain and the paleovalley of the desaguadero fluvial system. the plain grades eastward and includes several longitudinal depressions (longitudinal valleys). a sandy silt mantle is covering the plain, whereas the main dune system is located along the longitudinal depressions and the desaguadero paleovalley (fig. 1). in the three studied areas two eolian units, informally named lower and upper, were identified. these units, separated by a buried soil, were generated by winds from the w-nw in santa isabel and from the s and sw in general acha. wind directions coincide with present wind systems. the upper part of the lower unit is modified by the development of a buried soil showing an a-c horizon sequence. this soil is only buried in areas deeply affected by anthropic activities. away from these impacted settings, the soil is on the present groundsurface. in toay, fossil remains of megath